Let's say you have a web app with some database. In your database you have an Invoice model, where you store things you are charging your customers. Your billing system is flexible, so you support setting up tax inclusive or exclusive invoices, as well as tax free invoices! In this model you store it as: #!pythonclassInvoice:...is_taxable:boolis_tax_inclusive:bool You use this for a couple of years, write a bunch of instances to your database. The one day you wake up and decide that you no lo...
